Systems that connect electronic components often use conductive pins and conductive, plated-through holes (PTHs). Typically, a system of this type includes an electronic component having a plurality of metal pins extending therefrom and another component having a corresponding plurality of holes to receive the pins when the two components are aligned with each other. The electronic components can include, for example, printed circuit boards (PCBs) and integrated circuits (ICs).
In order to connect the two components, a housing of the component including the pins and a housing of the component including the holes are brought together to insert the pins into the holes. To form a secure connection between the pins and the holes, a solder-less “compliant fit” approach can be used. With this approach, each pin can be flat (e.g., with a square or rectangular cross-section) and include a hole (or eye) stamped through the pin, like an eye of a needle used for sewing. A pin used with this approach is an example of what is more generally referred to herein as a compliant pin, and is able to be compressed when inserted into a hole to form a secure connection. More specifically, a cross-sectional diameter of each pin is larger than the cross-sectional diameter of its corresponding hole to provide an interference or press-fit when the pin is inserted into the hole. The compressed pin applies pressure against inner electrically conductive surfaces of the holes to provide a secure mechanical and electrical connection.
Compliant pin dimensions have been increasingly scaled down. Miniaturization of compliant pins creates manufacturing difficulties due to tolerance issues. Imperfections in the shape of a pin (e.g., asymmetry) due to these tolerance issues can result in too much unwanted deformation of a compliant pin when the pin is inserted into a hole (e.g., in a circuit board), causing reduced normal force between the pin and the barrel of a hole into which the pin is inserted. Thus, the retention force of the pin in its hole is degraded, and performance of a product including the compliant pins decreases. For example, known compliant pins may exhibit unwanted plastic deformation and not enough elastic deformation. Plastic deformation refers to a type of irreversible deformation, which occurs in materials after stresses have attained a certain threshold value, such as the elastic limit or yield stress. Elastic deformation refers to a type of reversible deformation. With elastic deformation, once forces (e.g., a stress field) are no longer applied, the object returns to its original shape. On the other hand, an irreversible deformation (e.g., plastic deformation) remains even after stresses have been removed.
Non-symmetrical shapes of pins can also cause a concentration of deformation and crack formation in critical zones of compliant pins having eye of the needle type openings when the pins are inserted into a hole. For example, a pin having an eye of the needle type opening may exhibit increased strain at a particular interval of stress to result in a crack, where strain is defined as the amount of deformation an object experiences compared to its original size and shape, and stress is defined as a force per unit area, such as tensile or compressive loading on an object. Reliability issues can occur in electronic interconnects including cracked pins.
Accordingly, there is a need for an improved compliant pin design that produces more reliable interconnects when using a compliant pin.